The present invention relates to a telephasing system and method for identifying an unknown phase within a polyphase network used for transmission or distribution of electrical energy, for example, a three-phase network, by comparison of the unknown phase with a known phase of the polyphase network. The system according to the present invention is especially designed for use when the known phase is located at a point of the network far from the point of the network where the unkown phase is located.
It should be noted that in the present disclosure and in the appended claims, the expressions "telephasing" and "phasing" relate to the determination or identification of unknown phases within a polyphase network.
The telephasing method and system according to the present invention allow the identification of unknown phases. For example, in the case of the addition of a line or the modification of the path or run of a line within a three-phase network. The system and method of the present invention allow the identification of unknown phases within the three-phase network when these unkown phases are located far from known phases of this same network. Such a method and system can also advantageously allow the staff responsible for the distribution of electricity to the consumers to identify the phases of the rural or urban distribution lines.
Up to now, the identification of such unknown phases in a three-phase network for transmission or distribution of electrical energy was made by carrying out one of the following methods, the choice of which was dependent on the specific variables of each given application. Some of these methods consist of an injection on one phase of a low voltage through a distribution transformer, an injection on one phase of a high frequency signal, a single phase closing of breakers or other disconnecting devices mounted on the three-phase network, or a use of phasing sticks, of a reference voltage of the electrical distribution network, or of voltage transformers.
Some of the above-mentioned different methods should be carried out with no voltage on the network, whereby the electricity consumers supplied through this network are deprived of electricity during relatively long periods (from one to a few hours). Moreover, in most of the cases, these methods involve risks for the staff and the equipment, and require a large staff.
There is known from Canadian Pat. No. 1,056,309 (White) granted on June 12, 1979, a communication system using one of the lines of transmission of electrical energy of a three-phase network. However, the object of such a system is not to identify the unknown phases of a three-phase network, but to establish a conmunication interconnection between many points of this three-phase network through one of its electrical energy transmission lines. It is evident that the different phases, at the interconnecting point of this communication system with the three-phase network, must be known in order to allow the establishment of the desired interconnection between these different points.
Other devices for determining the sequence of the phases in a three-phase system are described in Canadian Pat. No. 1,054,225 (Vandevier et al), and U.S. Pat. Nos. 3,156,868 (Murrills), 3,555,417 (Mitchell) and 3,764,904 (Drexler). However, such devices do not allow the identification of the phases of a three-phase system when all the three phases of this system are unknown.